Larger displacement Atkinson cycle engines may be in the future for Toyota

A number of automotive manufacturers have begun to move away from larger displacement naturally aspirated engines to smaller displacement turbocharged engines. The general idea was that smaller and lighter engines would use less fuel while offering the same sort of performance thanks to the addition of a turbocharger. However, in the real world many drivers have discovered that turbocharged small displacement engines are often unable to deliver on their fuel efficiency claims.

Toyota is considering bucking the industry trend and rather than going with smaller turbocharged engines, is considering larger naturally aspirated engines to improve fuel efficiency. Senior managing officer in charge of drivetrain R&D for Toyota Koei Saga recently said that Toyota believes gasoline engines could benefit more from upsizing capacity in conjunction with Atkinson combustion cycles than going smaller with turbochargers.

Increasing the displacement of an engine using the Atkinson cycle would deliver a specific output less than that of similarly sized conventional combustion cycle engines, but fuel economy would be better. Toyota believes that fuel economy would be better than the smaller engines they replace.

Toyota has offered no timeframe for bringing larger displacement Atkinson cycle engines to market and hasn't hinted at which models might get the Atkinson cycle engines.

Mazda experimented with similar “delayed valve” Miller Cycle technology over a decade ago in the Millenia midsize sedan. But instead of using electric motors to make up for the reduced power density like today’s Atkinson-engine hybrid vehicles, the Millenia used a supercharger.

Saga also talked a bit about the next generation Toyota Prius saying that the vehicle will use a mixture of battery technology including lithium-ion and nickel batteries. The reason for mixing battery types is that lithium-ion batteries are better for performance, but the durability and lifespan is better for nickel batteries.

I feel the same way, plus I live in Colorado and drive between 5500ft and 12000ft elevation. Did you known that naturally aspirated engines lose 3% of their max horsepower for every 1000ft above sea level that they're driven? This starts to matter when you live at 8700ft and need to literally climb mountains. Turbocharged engines make for a happy engine in Colorado.